[NF] Discord Integration 2.8.7

Initial support for XenForo 2.3.

- Harden function to get Discord server mapping.
- Fix group sync position tracking not being displayed correctly.

• Add initial support for cross-posting content to Discord forum channels.

• Adjust column types for various columns to account for older MySQL versions.
• Fix "Include replies made to threads" option not being set.
• Fix "Enable syncing of XenForo bans with Discord bans" was not respected.
• Fix new/re-opened report notifications being flipped.